Marble or Granite shelfs in a hifi rack?

Here is what I believe.

In theory the best shelf will achieve two, mutually exclusive things. First that it is light and rigid. Second that it is damped.

Light and rigid is vital to ensure vibration energy is dissipated quickly. If you use a heavy shelf then energy will be stored and released slowly thereby smearing the music in the time domain. Some people like this effect since it results in a weightier bass, albeit less articulate and with incorrect pitch. If you use a floppy shelf you will get a similar effect, but that will be more focussed on a single frequency than a more rigid shelf. The "easy to come by" light and rigid shelves, such as glass are still fairly heavy, and they tend to ring badly.

Damped is important to avoid the release of energy being focussed on one frequency range. This is the problem when you use stuff like glass, granite, acrylic and corian. Corian is the best of these but smears the bass and still has a resonant peak. Those shelves that are not well damped tend to need to sit on bumpers rather than spikes - simply to avoid the resonances in the metal rack setting off resonances in the shelf. But the problem is that in not using spikes you will get more smearing of the sound due to energy storge in the rack.

So the ideal is a very rigidly welded steel rack (check that welding is more than one tack weld per join), spiked onto the floor; spikes screwed into the rack, supporting the shelf. The rack would ideally be put together with non-uniform shape - which is the principle that Sistrum focusses on. The shelf would be an ideal blend of light, rigid and damped - which is the ideal that Neuance aims for, and does a pretty good job of.

There are many shelf products and isolation devices that go in a different direction altogether. For example there are the Symposium style heavy and heavily damped products, which aim for neutrality and black background, but give up on speed. If your musical values include PRAT, then do not go this path. By the way I reckon a lack of understanding of PRAT is the principle reason for boring music systems. Many audiophiles listen for impact, detail and neutrality, but find it hard to listen for PRAT. PRAT is all about whether or not your system can communicate the rhythm and swing in the music and tends to require minimum smearing of transients, which tends to be most damaged by heavy support shelves and racks. The reference to Maple above is a decent example of this - the sound is reasonably neutral, but the mass means PRAT is badly compromised. I think PRAT is overlooked because in our straining to hear differences between stuff, we focus on the most easily discerned differences which are tonal colorations, impact and detail.

There are also many footer products that try to compensate for a bad rack. The hard footers are OK but are not very neutral and only have a significantly beneficial effect when you have put too much mass in your shelf/rack. The soft footers suffer the same problem as the 'less than rigid' shelf - they channel energy into a frequency range. Many of these claim, as do the bladder products, to channel the energy into very low frequencies that do not affect the sound. They do not affect neutrality, or detail, but they generally sound 'swimmy' and indistinct - in my opinion because they allow lateral movement, which is the worst form of energy for stereo equipment in my experience.

So the simple message is that Granite is way too expensive for its performance as a shelf, and I recommend you look elsewhere.

Excellent post Redkiwi. Non-resonant material is critical, I think. Maybe more important than absorbing vibrations.

Resonance is the natural frequency of a material. I'm thinking when music hits this frequency it will sound very unnatural. Or worse, this resonant frequency could be in the music all the time making strange tonality etc.
Resonances are much greater in intensity than vibrations coming through the floor etc. which are not at the resonant frequency of the base / component / etc.. So I'm thinking this is the first problem that needs to be fixed. Isolation is secondary.

While air bladders and sorbothane may absorb vibrations they are not a rigid mounting base and I'm guessing could create resonances or bad vibrations at some other frequency.

Noting Redkiwi's caution with Maple, maple seems pretty non-resonant and it is hard (compared to rubber or air bladders). So my next experiment will be setting the CDP directly onto 2) 2-3" wide x 1- 1 1/2" thick hardwood like maple.

Why bother with footers which just cost money and could add resonances of their own? I think direct coupling the CDP to the wood would be better. Large contact area / direct transfer. Also mass load the CDP with brass on top or brass sitting on wood sitting on CDP.

Also Redkiwi's post seems to say the ceramic foot polishing stones in the beauty section of Wal-Mart are the perfect footer solution.

I commend Redkiwi on his efforts to form a consistent analysis of vibration and its effects, based on years of experimentation with different materials and theories. I don't disagree with his anaylsis but would add an important caveat - that you test your own equipment on the types and kinds of platforms before going wholesale for one approach or another.

I own a Spectral system, with mostly MIT a/c treatment and cables, including isolation transformers on each of the 3 front end components (transport,dac, preamp). I use Zoethecus equipment stands (hard maple; heavy, layered, damped shelves of several grades;some shot fill in the legs) that I acquired 10 years ago when I first got into Spectral, and sold routinely by most U.S. Spectral dealers. I don't know whether Spectral is 'voiced' on Zoethecus or not. I also own several Symposium ultra's (heavy, damped), several Neuance shelves (light rigid), and any number of cones, shelves, and hats, and have played extensively with combinations of all of the above, plus other stands, over numerous years.

Spectral/MIT is a solid state system designed as very wide band and very detailed. My current system, using Symposium ultras as amp stands and basically Zoethecus equipment racks, has simply outstanding PRAT. It is also very musical, relaxed and non-edgy for solid state.

I find that there are any number of ways to drive the system into being far too analytic, and this almost always means the intensification of high frequencies to the point of non-listenability. Cones, the wrong stands (in my experience, Grand Prix for example), the wrong choice of rack material under individual components can kill the system sound. This is one reason why I think many people post about systems like Spectral sounding too analytic in some dealerships. Retail dealerships don't have the time to fuss with refining the system sound to the nth degree.

Unfortunately, products like Neuance shelves, which are broadband and not peaky in themselves, still have the effect of intensifying high frequencies, presumably by eliminating far more vibration than shelves like the denser Zoethecus shelves do. (Neuance in this case is used as a supplementary shelf sitting on top of upturned cones atop any of the Zoethecus regular shelves, or in place of Zoethecus shelves altogether, or sitting on the floor on top of cones. It is also a general result pertaining to use of Neuance with the preamp, power supplies, and a/c treatment (the places where it has the most effect.)

I am not posting this in order to criticize Neuance, which I have found very useful with, for example, less exemplary players than Spectral, or to imply that detailed solid state gear has too many high frequencies as part of the signature that need to be 'smeared away' with vibration. (Although isolation transformers produce some inherent high frequencies of their own, which may be part of the problem.) The point is to say, again, do characterize your own equipment and its properties regarding vibration, prat, musicality etc. This is also part of the fun in understanding audio equipment.

Flex, if you're saying that the Neuance shelves don't work for you, that's the same results I had. Placed under my Io (all tube) phono stage, the system went completely lifeless.

What does work is the custom aluminum stand I had constructed, with stainless steel spikes to my slate floor. On top of the four post stand is four mod squad soft shoes (EAR group manufactured). On the squad feet sit a 2" slab of granite. On the granite is 12 of the smaller ISO Bearings, and on the ISO Bearings sits my phono stage. On top of the phono stage sits a 6 pound plastic box filled with lead shot and wrapped with layers of black cloth tape.

This combination has wonderful dynamics, is immune to foot falls and the sonic attack of my large speakers, which sit less than twelve feet in front of the stand.

My opinion is that every room and every type of equipment is different in the personality it presents when matched to various materials. The granite used here for instance, when substituted with maple butcher block, looses dynamics. When the granite is removed and the phono stage is coupled directly to the stand with mod squad feet, Walker cones or other direct coupling methods, the isolation is not near as good.

I am not advocating that everyone follow my set up. I am saying that there is not a universal truth as to what will work with every piece of equipment in every room. Best that each takes a bit from the forums and experiments to find what works.